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Answer to last week’s Question

Answer to last week’s Question. How long have physicists known that there were more than just protons, neutrons, electrons, and photons? A) 5 years B) 25 years C) 60 years D) 100 years. C. New Particle Physics. Lecture 12. Group 12. Isaac Gonzalez Michael Lomino Gray Slater

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Answer to last week’s Question

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  1. Answer to last week’s Question How long have physicists known that there were more than just protons, neutrons, electrons, and photons? A) 5 years B) 25 years C) 60 years D) 100 years C Lynn Cominsky - Cosmology A350

  2. New Particle Physics Lecture 12 Lynn Cominsky - Cosmology A350

  3. Group 12 • Isaac Gonzalez • Michael Lomino • Gray Slater • Hiromi Young Give it up for Group 12! Lynn Cominsky - Cosmology A350

  4. Today’s lecture Big Bang Timeline We are here Lynn Cominsky - Cosmology A350

  5. The Vacuum Era • Planck era • 10-43 s after the Big Bang • Temperature (kT) ~1019 GeV • Beginning of time – time and space are no longer separate entities • Emergence of spacetime • Inflationary era (lecture 14) • < 10-10 s, kT ~ 100 GeV • Vacuum energy dominates, driving Universe to enormous size • Fluctuations may be formed that eventually turn into large scale structure Lynn Cominsky - Cosmology A350

  6. Radiation Era • Creation of Light • >10-36 s after Big Bang - kT ~ 100 GeV • Vacuum energy turns into light, and equal amounts of matter vs. anti-matter • Gravitational attraction begins • Background radiation energy originates • Dark matter may be formed Lynn Cominsky - Cosmology A350

  7. Radiation Era • Creation of Baryonic Matter (Baryogenesis) • >10-36 s after Big Bang • Temperature (kT) ~ 100 GeV • A small excess of quarks and electrons is formed (compared to anti-quarks and anti-electrons) • Electroweak (Unification) Era • 10-10 s after the Big Bang, kT ~ 100 GeV • Forces and matter become distinguishable forms of energy with different behavior • Masses of particles are defined • May include baryogenesis Lynn Cominsky - Cosmology A350

  8. Radiation Era • Strong Era • 10-4 s after the Big Bang - kT~ 0.2 Gev • Quark soup turns into neutrons and protons • Dark matter may be formed • Electroweak Decoupling • 1 s after the Big Bang - kT ~ 1 MeV • Neutrons and protons no longer interchange (leaving 7 p for each n) • Cosmic neutrino background is formed • Electrons and positrons annihilate, adding energy to the cosmic background radiation, and an excess of electrons Lynn Cominsky - Cosmology A350

  9. Radiation Era • Creation of light element nuclei • 100 s after the Big Bang – kT ~ 0.1 MeV • Nucleosynthesis begins as neutrons and protons are cool enough to stick together to form Helium, some Deuterium, and a little bit of Lithium • Precise elemental abundances are established • Radiation Decoupling • 1 month after the Big Bang – kT ~ 500 eV • Interactions between matter and radiation are fewer and farther between • Blackbody background spectrum is determined Lynn Cominsky - Cosmology A350

  10. Field Theories • 1865 – James Maxwell unifies electricity and magnetism in the first field theory • Fields were proposed to explain how forces are carried between particles • Einstein’s theory of General Relativity is another example of a field theory electromagnetic wave Lynn Cominsky - Cosmology A350

  11. Particles and Fields • Fields carry energy through spacetime • Fields are present everywhere, including the vacuum (which is the lowest energy state of all the fields) • Fields can act like both waves and particles • Wave-like fields are called forces • Particle-like fields are called matter or photons • Matter interacts with other matter through forces Lynn Cominsky - Cosmology A350

  12. Quantum Electrodynamics • Quantum mechanics describes the laws of motion of sub-atomic particles • Interactions between sub-atomic particles are described by quantum field theories • QED is the quantum field theory which describes electromagnetic interactions at the sub-atomic level • Predictions from QED calculations are accurate to one part in a trillion Lynn Cominsky - Cosmology A350

  13. Feynman diagram for a electromagnetic interaction Quantum Electrodynamics • The 1965 Nobel prize for QED was awarded to Richard Feynman, Julian Schwinger and Sin-Itiro Tomonaga • Feynman diagrams are used to show the relation between particles and force carriers for all four forces Lynn Cominsky - Cosmology A350

  14. Feynman diagram of a weak interaction Electro-weak Unification • 1979 Nobel Prize awarded to Steven Weinberg, Abdus Salam, and Sheldon Glashow for the development of a unified field theory of electroweak interactions • They predicted the W and Z bosons (which were discovered in 1983, Nobel in 1984 to Carlo Rubbia and Simon van der Meer) Lynn Cominsky - Cosmology A350

  15. Electro-weak Unification Q: If the electromagnetic and weak interactions are really two sides of the same coin, then why are the W and Z particles so massive (80 GeV) while the photon is massless? A: In the early Universe, when the characteristic energy kT > 80 GeV, the electromagnetic and weak forces were united. As the Universe cooled out of the electroweak era, spontaneous symmetry breaking occurred which split out the W and Z Lynn Cominsky - Cosmology A350

  16. Spontaneous Symmetry Breaking • Balance a pencil on its tip – it has an equal chance to fall over in each direction. But when it falls over, it chooses a specific direction, and breaks the initial symmetry • Hydrogen and oxygen are symmetric molecules, yet when they combine to make water, the molecule has a characteristic angle of 105 degrees between the Hydrogen atoms. Lynn Cominsky - Cosmology A350

  17. Symmetries • Physical laws display mathematical symmetry • Rotate a square through space by 90o - it will look exactly the same • Rotate a circle by any angle – it will also appear the same • Because a circle has more choices of rotation angle, it is said to have a larger symmetry • Physical laws can be invariant with respect to changes in location, time or other types of transformations (rotation, velocity, etc.) Lynn Cominsky - Cosmology A350

  18. Symmetries • Patterns in the properties of particles can be described by mathematical symmetries which act on internal spaces – properties of the particles themselves, rather than its spacetime environment • Protons and neutrons are regarded as two different directions in an abstract internal space – although their charges are different, they have identical strong interactions • This is another example of a broken symmetry which is thought to be unified at higher energies Lynn Cominsky - Cosmology A350

  19. Quantum Chromodynamics • QCD is the quantum field theory which describes the interactions between quarks and gluons • It is difficult to use QCD to make predictions because the gluons carry a color charge and interact with each other • QCD is a non-linear theory which can only be calculated approximately - 10% accuracy for mass of proton – calculations take months of supercomputer time Lynn Cominsky - Cosmology A350

  20. ddd ddu duu uuu D- Do D+ D++ dds dus uus S- So S+ = charge greater mass dss uss X- Xo sss W- Quantum Chromodynamics • 1969 Nobel to Murray Gell-Mann for quark classification scheme • Internal symmetry in the pattern of quarks predicted the W- particle and its mass Lynn Cominsky - Cosmology A350

  21. Gauge Theories • Gauge theories are quantum field theories that have local symmetries  physical laws remain the same when particle properties are exchanged at different locations in spacetime • Local internal symmetries actually require force carrier particles whose interactions create the forces • QED is an Abelian gauge theory • Electro-weak Unification is a non-Abelian gauge theory (1999 Nobel to t’Hooft and Veltman) Lynn Cominsky - Cosmology A350

  22. Put a pen on the table. Rotate it by 90o then by 180o Now start over but this time rotate it by 180o then by 90o Abelian Transformations 2D rotations are the same in either order Lynn Cominsky - Cosmology A350

  23. Put a pen on the table. Rotate it by 90o so the tip points to the floor then by 180o so the tip points up Now start over but this time rotate it first by 180o then by 90o – you get a very different result! Non-Abelian Transformation 3D rotations are not the same in either order Lynn Cominsky - Cosmology A350

  24. Beyond the Standard Model • Standard model describes every particle and interaction that has ever been observed in a laboratory • It has 18 arbitrary constants that are put in “by hand” – where do these come from? • The masses of the W and Z particles are not easily predictable from the Standard Model • The Standard Model also does not predict the pattern of masses and the generational structure – is a new symmetry needed? Lynn Cominsky - Cosmology A350

  25. 18 Free Parameters • Fundamental electroweak mass scale (1) • Strengths of the 3 forces (3) • Masses of e-, m and t (3) • Masses of u, c and t quarks (3) • Masses of d, s and b quarks (3) • Strength of flavor changing weak force (3) • Magnitude of CP symmetry breaking (1) • Higgs boson mass (1) Lynn Cominsky - Cosmology A350

  26. strong weak 1016 GeV electromagnetic Grand Unification of Forces • Strengths of three forces depend on the energy at which the observations are made • Supersymmetric theories can unify the forces at higher energies than we can observe Lynn Cominsky - Cosmology A350

  27. Relativistic Heavy Ion Collider • Brookhaven National Laboratory • Collides gold ions to form quark-gluon plasma to simulate Big Bang conditions • QGP has never been made on Earth but should exist inside neutron stars Lynn Cominsky - Cosmology A350

  28. RHIC movie Lynn Cominsky - Cosmology A350

  29. RHIC Quark-Gluon Plasma RHIC collision simulation movies Lynn Cominsky - Cosmology A350

  30. RHIC Quark-Gluon Plasma • Movie shows particle collision as seen by PHENIX experiment Lynn Cominsky - Cosmology A350

  31. RHIC Quark-Gluon Plasma Lynn Cominsky - Cosmology A350

  32. Supersymmetry • Supersymmetry is a larger symmetry that treats the 3 forces as broken pieces of a larger whole, and can predict all the properties and interactions of the particles • Predicts a combination of g1 and g2 that agrees with what is measured in the electroweak unification regime (slide 26) • Predicts supersymmetric particle partners for each existing particle (the lightest “sparticle” is also known as a WIMP) Lynn Cominsky - Cosmology A350

  33. Supersymmetry • Sparticles have not yet been seen, but require experiments which can get to energies near 1 TeV • GUTs allow the conversion of quarks to leptons through the exchange of a very massive particle • Since protons are made of quarks, this interaction would cause protons to decay • Non-supersymmetric GUTs predict short lifetimes for protons, and have been ruled out Lynn Cominsky - Cosmology A350

  34. SuperK detector Proton Decay • Supersymmetric predicted proton decay rate is a few per year per 50,000 metric tons (SuperK volume) • SuperKamiokande finds a proton lifetime > 1033 years (no events are seen in over three years study of a huge volume of protons) – can eventually reach 1034 years Lynn Cominsky - Cosmology A350

  35. SuperK simulated data Proton Decay • p  e+po • po  2g, each produces an EM shower • e+ also produces an EM shower Lynn Cominsky - Cosmology A350

  36. Neutrino Oscillations • A pion decays in the upper atmosphere to a muon and a muon neutrino • Neutrinos oscillate flavors between muon and tau Lynn Cominsky - Cosmology A350

  37. D (m2c4) = 0.005 eV2 Neutrino Oscillations • High energy neutrinos that travel a short distance do not change their flavor • Low energy neutrinos that travel a long distance have a 50% chance of changing flavors Lynn Cominsky - Cosmology A350

  38. Neutrino Oscillations • K2K (KEK to SuperK) is the new experiment testing neutrino oscillation results • Neutrinos produced at KEK are measured at near detector and then shot 250 km across Japan to SuperK detectors • First events are now being detected – 38 in near detector vs. 28 in far detector – not quite enough to prove oscillations Lynn Cominsky - Cosmology A350

  39. Origin of Mass • Electroweak unification predicts the existence of yet another particle, the Higgs boson • The Higgs boson is a neutral particle with zero spin which is the force carrier for the Higgs field • The Higgs boson breaks the electro-weak symmetry which gives the W and Z much heavier masses than the photon • Interactions with the Higgs field are theorized to give mass to all the other particles  “cosmic molasses” Lynn Cominsky - Cosmology A350

  40. Higgs Boson • Supersymmetry predicts the Higgs mass should be less than 150 GeV • Present CERN LEP limits are that it must be greater than 90 GeV – hint for 115 GeV • Fermilab limits will be 130 GeV by 2002 • CERN’s LHC can reach 150 GeV by 2010 • Looking for the Higgs was the goal of the (now-cancelled) Superconducting SuperCollider • Higgs boson is aka the “God Particle” Lynn Cominsky - Cosmology A350

  41. CP Violation • CP means “charge-parity”, aka time-reversal symmetry – the symmetry that results from interchanging a particle with its anti-particle and sending it through a 3D mirror • CP violations were first observed in decays of K-mesons vs. anti-K-mesons – the decays happened at different rates (1980 Nobel, James Cronin and Val Fitch) • Studies of flavor changing interactions with K and B mesons should tell us more about CP physics Lynn Cominsky - Cosmology A350

  42. Generation structure of weak force CP Violation • Strongest part of the weak force does not change generations • Weaker parts of the weak force allow changes in quark generations • There are 3 parameters which describe the strength of generation (“flavor”) changing weak force Lynn Cominsky - Cosmology A350

  43. CP Violation • Kaons oscillate between two types– short-lived (green) which decay into 2 pions and long-lived (red), which decay into 3 pions • Both indirect and direct CP violation have now been observed, • The weak force is being held responsible Lynn Cominsky - Cosmology A350

  44. Theory of Everything • Mathematical unification of gravity with the other 3 forces (which are governed by quantum mechanics) • Einstein was the first to try (and fail) to develop a ToE • Supersymmetry theories are low-energy extensions of superstring theories • Superstring theories are the most promising approaches to ToEs (see Lecture 13) • Anthropic principle - physical forces and constants are precisely balanced to allow life Lynn Cominsky - Cosmology A350

  45. No hydrogen survives Big Bang We are here No stable elements Precise force balance Why does the Universe behave the way it does? Lynn Cominsky - Cosmology A350

  46. Anthropic Principle • Is this balance an accident or part of a grand design by a grand designer? • Two opposing views: • If the laws of physics completely explain the creation of the Universe, then what role would there be for a Creator? (Hawking) • If there really is a ToE, then the beauty and order of the physical laws indicate that a Creator must have originated the laws (Davies) Lynn Cominsky - Cosmology A350

  47. What are the next questions? • What is the origin of CP violation? Is a new force involved? If not, what will we learn about the weak force? • Will we soon find the Higgs boson? • Are there more conservation laws? Is lepton number conservation strictly upheld? • Do protons actually decay? If so, what is their lifetime? • Do neutrinos oscillate? What is the mass of each generation of neutrino? • How will quark-gluon plasma behave? Lynn Cominsky - Cosmology A350

  48. Web Resources • The Particle Adventure http://particleadventure.org/ • Georgia State University Hyperphysics http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html • National Research Council study of Elementary Particle Physics http://www.nap.edu/readingroom/books/particle/#contents • Boston University HEP site http://hep.bu.edu • Nobel Prizeshttp://www.nobel.se • Brookhaven National Laboratory (RHIC) http://www.rhic.bnl.gov Lynn Cominsky - Cosmology A350

  49. Question of the Week • Do you think there is a cosmic Creator? • Yes, and the Creator was responsible for fine tuning the laws of physics to allow life • B) Yes, and the Creator is still responsible for the entire Universe • C) No, the physical laws just happened by accident • D) This question can’t be answered with the available data Lynn Cominsky - Cosmology A350

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